The study will be a prospective, randomized, multi-centre study with 3 parallel-intervention arms and blinding of outcome assessors. Subjects will be randomly allocated to 1 of 3 exercise-training arms: CT80, CTVT, or IT. The duration of the training phase will be adjusted for each arm such that the total amount of work will be equivalent to each arm. Training intensity will be ascertained with heart rate (HR) monitors. The frequency and length of training were chosen based on latest pulmonary rehabilitation (PR) guidelines. Upon completion of the 12-week intervention, subjects will be given standardized exercise recommendations to follow at home or in the community until their 1yr follow-up. Assessments will be made at baseline (week 0), program completion (week 12) and 1yr after program initiation (week 52). Randomization of groups of 6 subjects will occur in block, once all 6 subjects have completed baseline assessments. The randomisation process will consist of a computer-generated random listing of the 3 treatment allocations blocked by groups of 6 and stratified by site. The research assistant will be responsible for randomization and for coordinating assessment and intervention visits with subjects, assessors and exercise-training supervisors. Subjects will be instructed not to talk about their group assignment to the assessors. Eligibility criteria are meant to differentiate COPD from other respiratory diseases and to ensure clinical stability and patient safety. Subjects will be recruited by a research assistant from at Sacré-Coeur and at Mount Sinai Hospital Montreal. Assessments will take place at Sacré-Coeur. Subjects will complete the intervention phase at Sacré-Coeur or at Concordia University. To date, 36 subjects have completed the study. As such, in order to achieve the targeted sample size, an additional 84 subjects will have to be randomized. We expect a recruitment rate of 25-30%. Thus, approximately 300 patients will have to be screened to meet the recruitment goal. Given that we were able to screen 200 patients over 2.5yrs of active recruitment, we anticipate that an additional 2.5yrs of recruitment from 2 sites will enable us to reach our target sample size. Follow-up measurements will require an additional 12months of data collection from the time the last patient is randomized. Accordingly, we anticipate total data collection to last 3.5yrs. We estimate that 10% of subjects will be lost to the week 12, while the number is expected to double at the week 52.